Article 2, Section 1, Clause 8 of the Constitution reads –

Before he enter on the Execution of his Office, he shall take the following Oath or Affirmation:–“I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States.”

I have this poster in my office. It is a reminder that the President takes an oath to “preserve, protect, and defend the Constitution of the United States.”